An amazingly useful feature would be an announcements feature either as a new page or in the overview.
It should look like news-feed-type page, listing all past announcements added by admins. Adding an announcement should work like adding a comment, perhaps with a title field, formatted with big bold letters in the feed. This will be useful when: making important changes to the repository folder structure, development workflow; test-server maintenance; updating an application build outside bitbucket.com (we keep our .exe, and .apk files in cloud storage so we don't overuse bitbucket's hosting hospitality ); etc.
Since the Overview page of the repository is so useful that everyone in my project just regularly checks the website repository page first for news about the development progress, it seems like a shame that I cannot globally announce important events here. REST API integration would also be perfect, so we can set up automatic announcements when adequate.